Method and apparatus for control of reeling

ABSTRACT

In the method for controlling reeling in a reel-up of a paper web, a paper web (W) is guided via a rotating reeling cylinder ( 1 ) around a reel spoil ( 2 ) into a reel (R) in such a way that the paper web (W) is passed onto the reel via a nip (N) between the reeling cylinder ( 1 ) and the reel (R). The paper web (W) running onto the reel is subjected to a load by means of actuators of the reel-up, which load affects the structure of the reel and is controlled by means of measured variables determined during the reeling process. A reel density is used as the measured variable, the reel density being determined during the reeling process continuously or at intervals, wherein it is possible to implement a closed control loop.

FIELD OF THE INVENTION

The invention relates to a method for controlling reeling in the reel-upof a web. The invention also relates to an apparatus for controllingreeling in the reel-up of a web.

BACKGROUND OF THE INVENTION

The reel-ups of web-like materials are used for reeling a materialpassed as a continuous web into a tight reel, so that it can betransferred to further processing. For example in reel-ups of a paperweb, a continuous paper web passed from a paper machine, coating machineor a corresponding paper processing apparatus is wound around a reelspool to form a reel. The web is brought onto the reel via a reelingcylinder which is arranged rotatable and against which the reel ispressed by means of a loading device provided in connection with thereel spool. Thus, the web enters the reel so that it is pressed inbetween the preceding layers of the reel and the mantle surface of thereeling cylinder. At this point, where the web enters in contact withthe preceding layers of the reel, the web is subjected to a particularnip load, linear pressure, produced by the aforementioned loadingdevice. In current reel-up types, the reel spool is also centre-driven,and by means of the torque of the reel spool it is also possible toaffect the peripherical force of the web to be reeled.

The reeling nip between the reeling cylinder and the reel is primarilyused to prevent air from entering the reel. By controlling the loadapplied to the web, it is, however, also possible to control thetightness of the roll that is building, and furthermore, the aim is tochange the load during the reeling so that at different points of theradius of the reel, the tightness of the reel would correspond to thequality requirements set in accordance with the paper grade andafter-treatment of the reel. The properties correlating with thetightness of the reel include reel hardness and reel density.

Methods for affecting the web in order to attain a suitable hardness ordensity distribution in the direction of the radius of the reel, aredescribed for example in the Finnish patent 71107 in which the reelspool rests on supporting rails and is loaded towards the reelingcylinder, and this loading force is adjusted in such a way that theloading force is reduced e.g. in accordance with a predetermined loadingprogram as the radius of the reel grows. When adjusting the loadingforce, one has to take into account the geometry of the loadingmechanism, which requires a separate sensor application therein so thatit is possible to make the necessary corrections when reducing theloading force. Moreover, other disturbing factors of the loadingmechanism and the loading device which affect the actual load of theweb, are disregarded.

Furthermore, the Finnish public patent application 884651 discloses amethod in which the mass of the web reeled around the reel spool iscontinuously calculated so that it would be possible to take intoaccount the effect of the weight of the reel when the reel is placedagainst the reeling cylinder before moving onto,the supporting railswhere most of the reel is formed.

OBJECTS AND SUMMARY OF THE INVENTION

The purpose of the invention is to present a method of a new kind forcontrolling the reeling process during the entire process of reelformation. The purpose of the method is to eliminate the disturbancefactors due to the mechanics, as well as other external disturbances,and to enable the reeling in such a way that each paper grade isprovided with the correct density in different parts of the reel.

The control of the reeling process utilizes the reel density as ameasured variable determining the load to be applied to the web. Thereel density of the formed reel can be determined by measurements andcalculations conducted with suitable sensors, either continuously or atsufficient frequent intervals.

Because the measured variable used is the reel density, i.e. thevariable which is the final objective of the reeling process, it ispossible to determine for each paper grade e.g. an optimal densitycurve, or, with respect to different purposes, optimal density curves asa function of the size (diameter or radius) of the reel. During thereeling process, this curve can be achieved as accurately as possible bytaking the reel density corresponding to each momentary size of the reelas a set value and by changing the load applied to the web in such a waythat this set value is attained.

Furthermore, the purpose of the invention is to present an apparatus forcontrolling the reeling process, by means of which the apparatus theaforementioned objectives to produce a reel with the desired densitydistribution are achieved. The apparatus constitutes a closed loop whichcomprises a calculating unit for calculating the reel density accordingto the measurement values issued by from a sensor, and a comparator andcontrol unit for comparing the value with the set value and foradjusting the manipulated variables affecting the density on the basisof the information.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in more detail withreference to the appended drawings, in which

FIG. 1 shows a side view of a reel-up of a paper web applying the methodaccording to the invention,

FIG. 2 shows a control principle schematically, and

FIG. 3 is an example of a guide curve on the reel density utilized inthe method.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows schematically a reel-up of a paper web, a so calledPope-type reel-up, which continuously produces paper reels from afull-width web W passed from a paper machine or the like, one full paperreel being marked with the letter R in the figure. A rotating reelingcylinder 1, i.e. a Pope cylinder, guides the web W onto the reel R. Theweb W runs onto the reel R to be reeled via a reeling nip N between thelayers lying just beneath in the reel R and the reeling cylinder 1. Thereel R, located on the other side of the reeling cylinder 1 as seen inthe travel direction of the web, is loaded against the reeling cylinder1 in the radial direction by means of loading devices 3, e.g. hydrauliccylinders, known as such. The reel R is centre-driven, i.e. a reel spool2 around which the reel R accumulates, is provided with a drive. Theends of the reel spool 2 are supported in a suitable way known as such.

The web W to be reeled onto the reel R is subjected to a load by meansof a loading device directing force to the reel spool 2, and the forcecan also be transmitted to the web W by means of a special mechanism,such as a reeling carriage V. The force of the loading device 3 producesa particular loading force in the reeling nip N. Because this nip issituated on an axially oriented line of the reeling cylinder 1, the termlinear load can be used for this loading force. A second force to bedirected to the web W is a peripheral force which can be altered bychanging the torque of the reel spool 2 that is being driven, and athird force affecting the web is web tension which can be produced bymeans of control devices associated with the web.

During the reeling process, the density of the reel R which isaccumulated around the reel spool 2 is determined continuously or atsuitable intervals. In this context, the term “determine” can beunderstood as being a combination of direct measurements andcalculations, because the density is not a variable which could bemeasured directly e.g. by means of one sensor. Basically, however, thedetermination can also refer to the act of measuring the densitydirectly, if such a system is or becomes available. The density of thereel at a given time is obtained by determining the change in the massof the reel R within a certain period, and by dividing it with thechange in the reel volume that has taken place within the respectiveperiod.

The change in the mass of the reel R can be calculated on the basis ofthe web width, grammage and web speed. The web speed can be derived fromthe rotational speed of the reeling cylinder 1 with a fixed diameter, orit can be measured in another way. The rotating speed of the reelingcylinder 1 is obtained from a sensor 4 measuring the rotating speed ofthe reeling cylinder, such as a tachometer, but it can also bedetermined in other ways. The width of the web W is a constant factor inthe determination of the mass. The grammage can also be a constant term,but, if necessary, it can also be measured for example by means of asensor located before the reeling cylinder 1. If the web speed ispresumed to be constant, it can also be included as a constant factor inthe calculation without departing from the basic concept of theinvention, and in this case basically only time needs to be measured.

The change in the volume of the reel within the same interval can, inturn, be measured by measuring the increase in the thickness of thereel, i.e. the change in the distance between the reel spool 2 and thereeling nip N. This can be done by means of a suitable distancemeasurement sensor 5 which measures the change in the position of thespool 2 with respect to the reeling nip N. The sensor can be coupled forexample between the reeling carriage V or any other structure movingalong with the reel spool 2 and the supporting frame of the reelingcylinder 1, and for this purpose it is possible to utilize anysufficiently accurate sensors providing the position information. Thesensor is advantageously a digital sensor, for example a high resolutiondigital absolute sensor. In case of digital sensors, an A/D converter isnot required. Typically, the absolute sensor gives absolute positioninformation because it is capable of reading a code which in eachlocation of the sensor unambiguously gives the position of the sensorwith respect to the part (code ruler) containing the code. Digitalabsolute sensors can also include sensors based on counting the pulsesgenerated by the relative movements of the sensor and the second part.Similarly, it is possible to measure the distance by using an accuratedistance measuring laser in which the measurement is conducted by meansof a light beam. It is, however, also possible to use analog sensorswhich have a lower resolution and require an A/D converter. Analogsensors can be based on a potentiometer or on an inductive measurement.Instead of the aforementioned measuring sensors measuring the change inthe distance (shift), the thickness of the reel can also be obtained bymeasuring the rotational speed of the reel spool 2 when the speed of theweb W is known, which web speed can be presumed to be constant ormeasured in the way described above.

The increase in the volume of the reel R is naturally obtained as avolume of that cylinder whose inner diameter is the diameter of the reelin the beginning of the volume change measurement, and whose outerdiameter is the diameter of the reel at the end of the volume changemeasurement. Here, the width of the web is naturally a constant factor.

The signal/signals obtained from the sensor 4 and/or other sensors usedfor measuring the change in the reel mass, are passed along a line 6 toa calculating unit 8 in which the change in the mass during themeasuring time is calculated, wherein one variable used in thecalculation is also the time elapsed. If, in addition to the web width,also the grammage and the web speed can be presumed to be constant, thechange in the mass is calculated on the basis of these constant factorsgiven to the calculating unit as well as the elapsed time. From thedistance measurement sensor 5 or another sensor used for measuring thechange in the volume, a signal is passed to the calculating unit 8 alonga line 7, by means of which signal the change in the volume iscalculated. On the basis of the received measurement signals, thecalculating unit 8 conducts calculations on the basis of which thedensity of the reel produced during the measuring time is obtained.According to this information, the comparator and control unit 9controls the loading device 3 affecting the nip pressure along a line10, as well as an actuator affecting the peripheral force along a line11, in accordance with an internal calculating method of the unit on thebasis of the set value of the reel density given to the comparator andcontrol unit.

The calculating unit 8 can also receive other information, which is notused for calculations to determine the density. It can also collectinformation from other sensors situated in connection with the reel-up,conduct calculations on the basis of this other information, possibly bycombining it with the information obtained from the aforementionedsensors used for determining the density, as well as record this otherinformation and/or the results of the calculations conducted by means ofthe other information.

The intervals in which the changes that have taken place are measured,can be very short, and the density measurements can be made at intervalsimmediately succeeding each other, wherein the density of the reel is,in practice, monitored continuously. The calculating unit can alsoprocess the value of the density based on the value of mass per volume(m/V) in order to produce a measured variable to be used for the actualadjustment; for example, it is possible to utilize filteringmeasurement. Thus, for example, the obtained value is supplemented witha certain portion of new dm/dV data in order to prevent the system fromfluctuating. Similarly, it is possible to supplement the calculatingunit 8 with a storing device 12 by means of which it is possible tostore the achieved density in a memory as a function of the thickness ofthe reel for future use of the reel.

The process is illustrated in the diagram of FIG. 2. In this context,the measured variable refers to a variable obtained from the process bymeans of various measurements and calculations, the value of thevariable being used for controlling the process. By means of theabove-presented principle, the reeling process becomes a closed controlloop, because the measured variable, the reel density, is obtained fromthe product of the reeling process, i.e. the machine reel, and thepredetermined ideal values of this variable can be used as set valuesfor the adjustment.

FIG. 3 shows one guide curve for the reel density, which curve is anempirically measured density curve as a function of the diameter. In thecurve, the density of the reel is indicated on the vertical axis and thethickness of the reel on the horizontal axis. The curve can also be morerectilinear, devised for example by means of an empirically attainedcurve. As can be seen in the figure, the general objective is that thereel density decreases when the radius of the reel increases, and eachpaper grade may have typical optimal curves (distributions of theoptimal density, in accordance of which the density of the reel isreduced when the reel grows). In accordance with the grade of the paperweb to be reeled, a guide curve for the reel density according to FIG. 3is entered in the comparator and control unit 9. The respective setvalue of the density is determined according to the thickness of thereel R at a given time, the thickness being obtained in theabove-described measurements, for example by means of the distancemeasurement sensor 5. Thus, the set value of the reel density used bythe comparator and control unit 9 changes when the radius of the reelchanges.

By means of the curve, it is possible to conduct the adjustmentaccording to the following principle:

1) density_(1,guide)=the value of the guide curve for the reel densitywhen the paper on the machine reel value is 1

density_(1,measured)=(mass₁/volume₁)=f(speed₁, web width₁,grammage₁)/f(diameter₁)

or more generally: density_(1,measured)=f(speed₁, web width₁, grammage₁,diameter₁)

→deviation value=density_(1,guide)−density_(1,measured)→linear loadguide=1

→peripheral force guide=1

2) density_(2,guide)=the value of the guide curve for the reel densitywhen the paper on the reel value is 1

density_(2,measured)=(mass₂/volume₂)=f(speed₂, web width₂,grammage₂)/f(diameter₂)

or more generally: density_(2,measured)=f(speed₂, web width₂, grammage₂,diameter₂)

→deviation value=density_(2,guide)−density_(2,measured)→linear loadguide=2

→peripheral force guide=2

In the method, the load directed to the web to control the reel densityis composed of the linear load in the nip and the peripheral force, andthese manipulated variables can be changed in ways described above bymeans of the actuators of the reel-up in order to change the reeldensity. The initial value of the peripheral force is a certain,predetermined portion of the web tension, and the initial value of thelinear load is the linear load upon closing the nip. The web tension ismaintained advantageously constant, but it can also be adopted as amanipulated variable in the process by means of a correspondingactuator. The peripheral force and the linear load are controlled forexample on the basis of empirical information, or by modelling aprinciple which is known to be useful.

By means of suitable reel-ups it is possible to map paper grade specificguide curves for the reel density, i.e. reference reel density curves,and when new reels of the same paper grade are reeled, these curves ortheir approximates can be used as optimal curves determining the setvalues. Furthermore, it is possible to determine different referencereel density curves for the same paper grade, the curves depending onthe further processing of the reel.

In the apparatus, it is possible to use known instrumentation and datatransmission solutions of process automatics. The calculating unit 8 andthe comparator and control unit 9 can constitute functional parts of afast computer used as a central processing unit for the apparatus, andas the storing device 12 it is possible to use the memory of thecomputer from which the information of each reel can be retrieved,copied or transmitted forward along data transmission lines.

The invention is not restricted solely to the solutions presented above,but it can be modified within the scope of the inventive idea presentedin the following claims. The invention includes all suitable knownsensor solutions and new future sensor types which can be used in thisinvention. Similarly, the invention is applicable to all materials inthe form of a continuous web, especially a paper web. In this context,the term paper web refers to all reelable webs of fibrous raw materialirrespective of the grammage.

What is claimed is:
 1. Apparatus for controlling a reeling process in areel-up of a paper web comprising: a reel spool (2) supported at leastat its ends, actuators for applying a load to the paper web runningthrough a reeling nip onto a reel (R) having a growing size around thereel spool (2), means for determining measured variables of the reelingprocess and means for controlling the actuators on the basis of thedetermined measured variables, wherein the means for determining themeasured variables comprise measuring sensors and a calculating unit (8)coupled to the sensors, said calculating unit being structured andarranged to calculate a reel density which is used as a measuredvariable, on the basis of measurement data transmitted by the sensorsfrom the reeling process, wherein the means for controlling theactuators comprise a comparator unit and control unit (9) which isconnected to the calculating unit (8), contains information on a desiredreel density in set values as a function of the growing size of thereel, and is arranged to compare the determined reel density with theset value and to control the actuators on the basis of the comparisons,wherein the actuators to be controlled comprise a loading device (3)affecting a linear load in the reeling nip (N) and/or an actuatoraffecting a peripheral force through a torque of the reel spool beingdriven, and wherein the information on a desired reel density in setvalues as a function of the growing size of the reel is a decreasingreel density with a growing size of the reel.
 2. Apparatus according toclaim 1, wherein the calculating unit (8) is arranged to calculate thereel density on the basis of the change in the mass and volume of thereel.
 3. Apparatus according to claim 2, wherein to determine the changein the volume of the reel (R), the measuring sensors comprise a distancemeasurement sensor (5) measuring the change in the size of the reel (R).4. Apparatus according to claim 3, wherein the distance measurementsensor (5) is a digital sensor.
 5. Apparatus according to claim 2,wherein to determine the change in the volume of the reel (R), themeasuring sensors comprise a sensor measuring the rotating speed of thereel spool (2) constituting the core of the reel.
 6. A method forcontrolling reeling in a reel-up of a paper web, comprising the stepsof: guiding a paper web via a rotating reeling cylinder around a reelspool into a reel in such a way that said paper web is passed onto saidreel via a nip between said reeling cylinder and said reel; subjectingsaid paper web running onto said reel to a load by means of actuators ofsaid reel-up, which loads affects the structure of said reel and iscontrolled by means of measured variables determined during said reelingprocess while said reel is supported at least at either ends of saidreel spool, wherein the density of said reel is used as a measuredvariable, said reel density being continuously determined or determinedat intervals, whereby in the control, the desired reel density as afunction of the size of said reel is used as a set value; controllingsaid load on said paper web by controlling the linear load effective insaid nip between said reeling cylinder and said reel and/or bycontrolling a peripheral force through a torque of the reel spool beingdriven; and wherein the desired reel density as a function of the sizethe reel is a decreasing reel density as a growing size of the reel. 7.The method according to claim 6, wherein determining the density of saidreel further comprises the steps of: determining the change in the massof said reel; determining the change in the volume of said reel; anddividing said determined change in mass by the determined change involume of said reel.
 8. The method according to claim 7, whereindetermining said mass of said reel further comprises the steps of:determining the width of said paper web; determining the grammage ofsaid paper web being reeled; determining the speed at which said paperweb is reeled onto said reel.
 9. The method according to claim 8,wherein said speed of said reeling is based on the rotational speed ofsaid reeling cylinder.
 10. The method according to claim 7, wherein saidstep of determining the change in size of said volume further comprisesthe steps of: determining the increase in thickness in the radialdirection of said reel web.
 11. The method according to claim 6, furthercomprising the step of: utilizing a paper-grade-specific guide curve,unique to said reel density used, determining set values for said reeldensity from said curves as a function of said reel's size and the gradeof said paper to be used.
 12. An apparatus for controlling reeling areeling process in a reel-up of a paper web, comprising: a reel spoolsupported at its ends; a plurality of actuators for applying a load tosaid paper web running onto a reel around said reel spool; means fordetermining measured variables of said reeling process; means forcontrolling said actuators relative to said measured variables, wherein,said means for determining said measured variables of said reelingprocess include a plurality of measuring sensors and a calculating unitcoupled to said measuring sensors, whereby, said calculating unit isarranged to calculate the density of the reel which is used as ameasured variable; wherein said means for controlling said actuatorsinclude a comparator and control unit connected to said calculatingunit, said control unit having information on the desired reel densityin set values as a function of the size of said reel and is structuredand arranged to compare said determined reel density with said set valueand to control said actuators based on said comparison; wherein saidactuators further comprise a loading device for affecting the linearload in said reeling nip and/or an actuator for affecting a peripheralforce through a torque of the reel spool being driven; and wherein theinformation on the desired density of the reel in set values as afunction of the size of the reel is a decreasing reel density with agrowing size of the reel.
 13. The apparatus according to claim 12,wherein the calculating unit is configured to calculate the density ofsaid reel on the basis of the change in the mass and volume of saidreel.
 14. The apparatus according to claim 13, wherein said measuringsensors further comprise a distance measurement sensor for measuring thechange in the size of said reel.
 15. The apparatus according to claim14, wherein said distance measurement sensor is a digital sensor. 16.The apparatus according to claim 13, wherein said volume measuringsensor comprise a sensor for measuring the rotational speed of said reelspool.